Alignment and repair systems

Jig brackets: general development

Vehicle design and manufacture have progressed

considerably over the years. The development of

crash repair systems has likewise mirrored these

changes. When cars were chassis built, the chassis

Figure 14.11Mitek system in use, with P188 Mk2 measuring system (Blackhawk Automotive Ltd )

Major accident damage 413

tended to be relatively flat, so that the repair was

mainly two dimensional. The change to lighter

monocoque construction introduced one other

dimension which demanded further consideration.

First, the height of the critical points on the

vehicle’s underside were controlled relative to an

imaginary datum line, and so height became of

vital importance. Second, accuracy became a far

more critical consideration than in the past, as

suspension systems became less adjustable and

more complex.

Jig brackets were introduced to serve as simple

go/no-go gauges, providing a continuous visual

indication of the extent of damage. During repairs

brackets were found to yield further benefits.

They provided progressive anchorage, meaning

that once a crititical point had been repaired and

locked in place with the jig bracket, it would not

be disturbed by subsequent repairs. In addition,

during building the jig brackets act as a welding

jig to ensure that new parts are correctly installed

and that the positions of important steering and

suspension pick-up points are not disturbed by

welding heat.

Concurrent with these developments, vehicle manufacturers

were concentrating on particular aspects

of car design. They were attempting to improve body

weight by the introduction of high-strength steels

and vehicle safety by incorporating strong passenger

compartments with front and back and crumple

zones to absorb impact on collision. These two

developments mean that cars are more susceptible to

damage in the crumple zone areas at the front and

rear ends as a direct result of the built-in safety characteristic

of deformation of structures. Consequently

more cars now need alignment and repair requiring

the use of jig equipment. In particular there has been

a growth in the number of cars sustaining damage

which, while not major, still requires the use of

proper diagnostic and repair systems to effect a

repair. The repairer must therefore choose the repair

system most appropriate to the degree of damage

present. Consequently there has been a growth in the

development of measuring systems which can be

used in a wide variety of repair situations with speed

and accuracy. With dual systems, which combine

both brackets and measurement, the repairer can

carry out fast and accurate repairs whatever the

degree of damage. However, with any body alignment

system, whether jig brackets or a measuring

system, it is vital that the completion of repair should

be followed by a full suspension and wheel alignment

check to make sure that the car is completely

roadworthy.

Since the early 1950s there has been considerable

progress surrounding jig brackets. On the technical

side, developments mean that the jig brackets are

now available for a wide range of vehicles, are

lighter, easier to use and more readily available. For

ease of use and to prevent possible errors, integral

brackets fit to a regular-spaced hole pattern on top of

five integral beams which are common in all integral

bracket sets. The front integral beams run longitudinally,

as do chassis legs, thus allowing first improved

access to the engine compartment, and second the

production of stronger, simpler brackets. All integral

sets incorporate a number of check brackets which

are fitted without stripping out mechanical components.

Each integral bracket carries a plate which

shows a reference number, which side of the jig it fits

to and which edge points forward.